Fix for KT-11969: ProGuard issue with private interface methods

#KT-11969 Fixed

compiler/backend/src/org/jetbrains/kotlin/codegen/FunctionCodegen.java

@@ -133,7 +133,7 @@ public class FunctionCodegen {
                            new FunctionGenerationStrategy.FunctionDefault(state, function));
         }
 
-        generateDefaultIfNeeded(owner.intoFunction(functionDescriptor), functionDescriptor, owner.getContextKind(),
+        generateDefaultIfNeeded(owner.intoFunction(functionDescriptor, true), functionDescriptor, owner.getContextKind(),
                                 DefaultParameterValueLoader.DEFAULT, function);
 
         generateOverloadsWithDefaultValues(function, functionDescriptor, functionDescriptor);

compiler/backend/src/org/jetbrains/kotlin/codegen/MemberCodegen.java

@@ -66,6 +66,8 @@ import org.jetbrains.org.objectweb.asm.commons.Method;
 import java.util.*;
 
 import static org.jetbrains.kotlin.codegen.AsmUtil.*;
+import static org.jetbrains.kotlin.codegen.JvmCodegenUtil.isJvm8Interface;
+import static org.jetbrains.kotlin.codegen.JvmCodegenUtil.isJvm8InterfaceMember;
 import static org.jetbrains.kotlin.descriptors.CallableMemberDescriptor.Kind.SYNTHESIZED;
 import static org.jetbrains.kotlin.resolve.BindingContext.PROVIDE_DELEGATE_RESOLVED_CALL;
 import static org.jetbrains.kotlin.resolve.BindingContext.TYPE_ALIAS;
@@ -375,7 +377,14 @@ public abstract class MemberCodegen<T extends KtPureElement/* TODO: & KtDeclarat
     private Type computeOuterClass(@NotNull CodegenContext<?> context) {
         CodegenContext<? extends ClassOrPackageFragmentDescriptor> outermost = context.getClassOrPackageParentContext();
         if (outermost instanceof ClassContext) {
-            return typeMapper.mapType(((ClassContext) outermost).getContextDescriptor());
+            ClassDescriptor classDescriptor = ((ClassContext) outermost).getContextDescriptor();
+            if (context instanceof MethodContext) {
+                FunctionDescriptor functionDescriptor = ((MethodContext) context).getFunctionDescriptor();
+                if (isInterface(functionDescriptor.getContainingDeclaration()) && !isJvm8InterfaceMember(functionDescriptor, state)) {
+                    return typeMapper.mapDefaultImpls(classDescriptor);
+                }
+            }
+            return typeMapper.mapType(classDescriptor);
         }
         else if (outermost instanceof MultifileClassFacadeContext || outermost instanceof DelegatingToPartContext) {
             Type implementationOwnerType = CodegenContextUtil.getImplementationOwnerClassType(outermost);
@@ -393,10 +402,17 @@ public abstract class MemberCodegen<T extends KtPureElement/* TODO: & KtDeclarat
     @Nullable
     private Method computeEnclosingMethod(@NotNull CodegenContext context) {
         if (context instanceof MethodContext) {
-            Method method = typeMapper.mapAsmMethod(((MethodContext) context).getFunctionDescriptor());
-            if (!method.getName().equals("<clinit>")) {
-                return method;
+            FunctionDescriptor functionDescriptor = ((MethodContext) context).getFunctionDescriptor();
+            if ("<clinit>".equals(functionDescriptor.getName().asString())) {
+                return null;
             }
+
+            if (((MethodContext) context).isDefaultFunctionContext()) {
+                return typeMapper.mapDefaultMethod(functionDescriptor, context.getContextKind());
+            }
+
+            return typeMapper.mapAsmMethod(functionDescriptor, context.getContextKind());
+
         }
         return null;
     }

compiler/backend/src/org/jetbrains/kotlin/codegen/context/CodegenContext.java

@@ -299,9 +299,14 @@ public abstract class CodegenContext<T extends DeclarationDescriptor> {
         return new AnonymousClassContext(codegen.getState().getTypeMapper(), descriptor, ownerKind, this, codegen);
     }
 
+    @NotNull
+    public MethodContext intoFunction(FunctionDescriptor descriptor, boolean isDefaultFunctionContext) {
+        return new MethodContext(descriptor, getContextKind(), this, null, isDefaultFunctionContext);
+    }
+
     @NotNull
     public MethodContext intoFunction(FunctionDescriptor descriptor) {
-        return new MethodContext(descriptor, getContextKind(), this, null);
+        return intoFunction(descriptor, false);
     }
 
     @NotNull

compiler/backend/src/org/jetbrains/kotlin/codegen/context/ConstructorContext.java

@@ -34,7 +34,7 @@ public class ConstructorContext extends MethodContext {
             @NotNull CodegenContext parent,
             @Nullable MutableClosure closure
     ) {
-        super(contextDescriptor, kind, parent, closure);
+        super(contextDescriptor, kind, parent, closure, false);
     }
 
     @Override

compiler/backend/src/org/jetbrains/kotlin/codegen/context/InlineLambdaContext.kt

@@ -27,7 +27,7 @@ class InlineLambdaContext(
         closure: MutableClosure?,
         val isCrossInline: Boolean,
         val isPropertyReference: Boolean
-) : MethodContext(functionDescriptor, contextKind, parentContext, closure) {
+) : MethodContext(functionDescriptor, contextKind, parentContext, closure, false) {
 
     override fun getFirstCrossInlineOrNonInlineContext(): CodegenContext<*> {
         if (isCrossInline) return this

compiler/backend/src/org/jetbrains/kotlin/codegen/context/MethodContext.java

@@ -39,16 +39,19 @@ public class MethodContext extends CodegenContext<CallableMemberDescriptor> {
     // Note: in case of code inside property accessors, functionDescriptor will be that accessor,
     // but CodegenContext#contextDescriptor will be the corresponding property
     private final FunctionDescriptor functionDescriptor;
+    private final boolean isDefaultFunctionContext;
 
     protected MethodContext(
             @NotNull FunctionDescriptor functionDescriptor,
             @NotNull OwnerKind contextKind,
             @NotNull CodegenContext parentContext,
-            @Nullable MutableClosure closure
+            @Nullable MutableClosure closure,
+            boolean isDefaultFunctionContext
     ) {
         super(JvmCodegenUtil.getDirectMember(functionDescriptor), contextKind, parentContext, closure,
               parentContext.hasThisDescriptor() ? parentContext.getThisDescriptor() : null, null);
         this.functionDescriptor = functionDescriptor;
+        this.isDefaultFunctionContext = isDefaultFunctionContext;
     }
 
     @NotNull
@@ -126,4 +129,8 @@ public class MethodContext extends CodegenContext<CallableMemberDescriptor> {
     public FunctionDescriptor getFunctionDescriptor() {
         return functionDescriptor;
     }
+
+    public boolean isDefaultFunctionContext() {
+        return isDefaultFunctionContext;
+    }
 }